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Phys Rev Lett. 2002 Sep 23;89(13):130801. Epub 2002 Sep 9.

High-sensitivity atomic magnetometer unaffected by spin-exchange relaxation.

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  • 1Department of Physics, Univerisity of Washington, Seattle, Washington 98195, USA.


Alkali-metal magnetometers compete with SQUID detectors as the most sensitive magnetic field sensors. Their sensitivity is limited by relaxation due to spin-exchange collisions. We demonstrate a K magnetometer in which spin-exchange relaxation is completely eliminated by operating at high K density and low magnetic field. Direct measurements of the signal-to-noise ratio give a magnetometer sensitivity of 10 fT Hz(-1/2), limited by magnetic noise produced by Johnson currents in the magnetic shields. We extend a previous theoretical analysis of spin exchange in low magnetic fields to arbitrary spin polarizations and estimate the shot-noise limit of the magnetometer to be 2x10(-18) T Hz(-1/2).

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